Cache architecture for comparing data

ABSTRACT

The present disclosure includes apparatuses and methods for a cache architecture. An example apparatus that includes a cache architecture according to the present disclosure can include an array of memory cells configured to store multiple cache entries per page of memory cells; and sense circuitry configured to determine whether cache data corresponding to a request from a cache controller is located at a location in the array corresponding to the request, and return a response to the cache controller indicating whether cache data is located at the location in the array corresponding to the request.

PRIORITY INFORMATION

This application is a Continuation of U.S. application Ser. No.15/691,859, filed on Aug. 31, 2017, which issues as U.S. Pat. No.10,303,613 on May 28, 2019, which is a Continuation of U.S. applicationSer. No. 14/293,521, filed on Jun. 2, 2014, which issued as U.S. Pat.No. 9,779,025 on Oct. 3, 2017, the contents of which are included hereinby reference.

TECHNICAL FIELD

The present disclosure relates generally to semiconductor memory andmethods, and more particularly, to apparatuses and methods for a cachearchitecture.

BACKGROUND

Memory devices are typically provided as internal, semiconductor,integrated circuits in computing devices or other electronic devices.There are many different types of memory including volatile andnon-volatile memory. Volatile memory can require power to maintain itsdata (e.g., user data, error data, etc.) and includes random-accessmemory (RAM), dynamic random access memory (DRAM), and synchronousdynamic random access memory (SDRAM), among others. Non-volatile memorycan provide persistent data by retaining stored data when not poweredand can include NAND flash memory, NOR flash memory, read only memory(ROM), Electrically Erasable Programmable ROM (EEPROM), ErasableProgrammable ROM (EPROM), and resistance variable memory such as phasechange random access memory (PCRAM), resistive random access memory(RRAM), and magnetoresistive random access memory (MRAM), among others.

A memory system can include a cache memory that may be smaller and/orfaster than other memory of the system (e.g., DRAM, NAND, disk storage,solid state drives (SSD), etc., which may be referred to as mainmemory). As an example, cache memory may comprise DRAM memory. A memorysystem can cache data to improve performance of the memory system.Therefore providing cache memory that delivers improved performance forthe memory system is desirable. Improving the latency and hit rate ofthe cache memory are performance characteristics that can provideimproved performance of the memory system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a block diagram of an apparatus in the form of asystem including a cache in accordance with a number of embodiments ofthe present disclosure.

FIG. 2 is a block diagram illustrating mapping of data from a memory mapof a memory device to cache in accordance with a number of embodimentsof the present disclosure.

FIG. 3 illustrates a cache entry in cache in accordance with a number ofembodiments of the present disclosure.

FIGS. 4A and 4B illustrate the contents of a page in cache in accordancewith a number of embodiments of the present disclosure.

FIG. 5 illustrates a command associated with an apparatus comprisingcache in accordance with a number of embodiments of the presentdisclosure.

FIGS. 6A-6B illustrate responses to a read command associated with anapparatus comprising cache in accordance with a number of embodiments ofthe present disclosure.

FIGS. 7A-7B illustrate responses to a write command associated with anapparatus comprising cache in accordance with a number of embodiments ofthe present disclosure.

DETAILED DESCRIPTION

The present disclosure includes apparatuses and methods for a cachearchitecture. An example apparatus that includes a cache architectureaccording to the present disclosure can include an array of memory cellsconfigured to store multiple cache entries per page of memory cells. Theapparatus can include sense circuitry configured to determine whethercache data corresponding to a request from a cache controller is locatedat a location in the array corresponding to the request, and return aresponse to the cache controller indicating whether cache data islocated at the location in the array corresponding to the request.

In a number of embodiments, the cache architecture of the presentdisclosure can provide multiple cache entries mapped on to the same page(e.g., row) in a memory device (e.g., a CDRAM device, STT-RAM device,PCM device, for example, among other memory devices), which can allowfor multiple cache entries to be checked in parallel on the memorydevice. In a number of embodiments, the cache architecture of thepresent disclosure can provide reduced energy consumption and/orimproved latency as compared to previous approaches. For example, in anumber of embodiments, comparison logic (e.g., comparators) can beembedded within sense circuitry, or elsewhere in the cache (e.g.,CDRAM), to perform comparisons of multiple cache entries in parallelwithout transferring data (e.g., tag data and/or cache data) out of theCDRAM (e.g., via an input/output (I/O) line). Tag data from commands canbe compared to tag data in cache entries of the CDRAM to determine ifrequested data is located in the CDRAM or if the CDRAM is ready to writedata corresponding to a command to the CDRAM. Performing suchcomparisons using sense circuitry on the CDRAM can allow the commands tobe executed without transferring data between the CDRAM and a cachecontroller, for instance. In a number of embodiments, a cachearchitecture can comprise dual (e.g., separate) interfaces (e.g., aninput interface and an output interface) used to receive commands and tosend responses.

In the following detailed description of the present disclosure,reference is made to the accompanying drawings that form a part hereof,and in which is shown by way of illustration how one or more embodimentsof the disclosure may be practiced. These embodiments are described insufficient detail to enable those of ordinary skill in the art topractice the embodiments of this disclosure, and it is to be understoodthat other embodiments may be utilized and that process, electrical,and/or structural changes may be made without departing from the scopeof the present disclosure. As used herein, the designators “M”, “N”,“P”, “R”, and “S”, particularly with respect to reference numerals inthe drawings, indicates that a number of the particular feature sodesignated can be included. As used herein, “a number of” a particularthing can refer to one or more of such things (e.g., a number of memorydevices can refer to one or more memory devices).

The figures herein follow a numbering convention in which the firstdigit or digits correspond to the drawing figure number and theremaining digits identify an element or component in the drawing.Similar elements or components between different figures may beidentified by the use of similar digits. For example, 120 may referenceelement “20” in FIG. 1, and a similar element may be referenced as 220in FIG. 2. As will be appreciated, elements shown in the variousembodiments herein can be added, exchanged, and/or eliminated so as toprovide a number of additional embodiments of the present disclosure.

FIG. 1 is a block diagram of an apparatus in the form of a system 100including a cache in accordance with a number of embodiments of thepresent disclosure. In FIG. 1, the cache can be a cache DRAM (CDRAM)device 110. In the example shown in FIG. 1, system 100 includes a memorydevice 120, a cache controller 112, a controller 122, a queue 104, andan interconnect bus 102. In a number of embodiments, the CDRAM device110, the memory device 120, the cache controller 112, the controller122, and the queue 104 may also be considered an apparatus. The CDRAMdevice 110 includes an array 118 of DRAM memory cells and sensecircuitry 119. The sense circuitry 119 can include a number of senseamplifiers 115 and comparison logic 117 (e.g., a number of comparators)used in association with executing commands received by the CDRAM device110. The CDRAM device 110 can be coupled to the cache controller 112 viainput interface 114 and output interface 116. The input interface 114can be used to receive information (e.g. commands and/or data) at theCDRAM device 110 from the cache controller 112. The output interface 116can be used to send information from the CDRAM device 110 to the cachecontroller 112.

In a number of embodiments, the memory device 120 can include an arrayof memory cells, such as DRAM memory cells and/or NAND memory cells, forexample, among other types of memory cells. The memory device 120 canserve as a backing store that stores data that can be cached by CDRAMdevice 110.

In a number of embodiments, the memory device 120 can be coupled to thecontroller 122 via bus 124. The bus 124 can be a shared bus 124 or cancomprise a number of separate busses (e.g., address bus, data bus,control bus, etc.) to transfer information between the controller 122and the memory device 120. In a number of embodiments, the system 100can include a number of memory devices (e.g., memory device 120) and anumber of controllers (e.g., controller 122) coupled together via bus124.

In a number of embodiments, the system 100 can be coupled to a host(e.g., host processor) and/or other memory devices (not shown) viainterconnect bus 102. The host and/or other memory devices can send dataand/or commands to the queue 104 via interconnect bus 102. The system100 can be a memory system that stores data in memory device 120 anduses the CDRAM memory device 110 to cache data from memory device 120.The system 100 can also cache data (e.g., in CDRAM device 110) receivedfrom a host and/or other memory devices via interconnect bus 102.

The system 100 can cache data by sending a command from the queue 104 tothe CDRAM 110, for example. The command can be a read command or a writecommand, for instance. The command can be transferred from the queue 104to the cache controller 112 and to the CDRAM 110 via input interface114. The commands transferred via input interface 114 can include acommand indicator, tag data (e.g., an address), and a transaction ID(TID).

In a number of embodiments, the CDRAM device 110 can process a readcommand by locating the particular cache entry (e.g., slot) indicated bythe read command address. The CDRAM device 110 can include multiplecache entries on a single page, which can allow multiple cache entriesto be checked by accessing (e.g., opening) a single page. In a number ofembodiments, a cache page can include multiple cache entries, whereineach cache entry includes a portion of cached data from a backing store(e.g., memory device 120). Example cache pages and cache entries aredescribed further below in association with FIGS. 2-4. The CDRAM device110 can read the data corresponding to the indicated cache entry and usecomparison logic (e.g., comparators) to determine if a validityindicator indicates data corresponding to the command is located at theaddress corresponding to the command, (e.g., if a valid bit of the cacheentry is set and if a block address of the read command address matchesthe block address bits of the cache entry). If the valid bit is set andthe block addresses match, then the slot can be considered a hit and theCDRAM 110 can return a suitable response to the cache controller 112 viaoutput interface 116. The response to the cache controller 112 caninclude a TID and the cache data corresponding to the cache entry.Including the TID in the response can allow the cache controller 112 toidentify the particular command to which the response corresponds. Forinstance, if the valid bit is not set and/or the block addresses do notmatch, then the cache entry can be considered a miss and the CDRAM 110can return a suitable response to the cache controller 112 via outputinterface 116 indicating the cache data requested in the read commandwas not located in the CDRAM 110. The response to the cache controller112 can include a TID, which can be used by the cache controller toidentify the particular command to which the response corresponds.

In a number of embodiments, the CDRAM device 110 can process a writecommand by locating the particular cache entry (e.g., slot) indicated bythe write command address. The CDRAM 110 can read the data correspondingto the indicated slot and use comparison logic located on the CDRAMdevice 110 to determine if a validity indicator indicates that validdata is located at the slot corresponding to the address in the command(e.g., if the valid bit in the slot is set and if the dirt bity in theslot is set). A determination that the valid bit is not set can indicatethe slot is not storing valid data, such that the data corresponding tothe write command can be written to the cache entry. A determinationthat the valid bit is set, but the dirty bit is not set can indicate thecache entry is storing valid data that is not different from the data ina backing store, as such the data from the write command can be writtento the cache entry. A response can be sent to the cache controllerindicating that the write has been completed. The response can include atransaction ID (TID) which can identify which particular command wascompleted. A determination that the valid bit is set and the dirty bitis set, can indicate that the data that is currently in the slot is tobe evicted. Subsequent to eviction of the data from the slot, the datacorresponding to the write command is written to the slot. A responsecan then be sent to the cache controller 112 that indicates the writehas been completed. The response can include a TID and also the data andthe address of the data that was evicted from the slot. The system 100can then return this evicted data to a backing store (e.g., memorydevice 120).

FIG. 2 is a block diagram illustrating mapping of data from a memory mapof a memory device to cache in accordance with a number of embodimentsof the present disclosure. The example shown in FIG. 2 illustratesdirect mapping of data from memory device 220 to CDRAM device 210. Thememory device 220 can include a number of blocks (e.g., block 234-0 andblock 234-(P−1)) and each block can include a number of pages (e.g. page230-0 and page 230-R) of memory cells. Each page of a block can becached to the same location in the CDRAM device 210. For example, thefirst page of a block (e.g., page 230-0 from block 234-0 or block234-(P−1)), can be cached to the first two pages of the CDRAM device 210(e.g., page 232-0 and 232-1). Data in locations M−1 to M/2 from page230-0 can be mapped and cached to page 232-1 of CDRAM device 210. In anumber of embodiments, one page from a memory device can be mapped tothe first two pages of a CDRAM device (e.g., if a page in the memorydevice is twice as big as a page in the CDRAM device). For example, a 4KB page of a particular memory device can be mapped into two 2 KB pagesof a CDRAM device. In FIG. 2, page 230-0 from memory device 220 ismapped to pages 232-0 and 232-1 in CDRAM device 210. The first half ofpage 230-0 is mapped to page 232-1 and the second half of page 230-0 ismapped to page 232-0. Also, in FIG. 2, the last page of block in memorydevice 220 (e.g., page 230-R) is mapped to the last two pages in CDRAM210 (e.g., pages 232-(S−1) and 232-S). The first half of page 230-R ismapped to page 232-S and the second half of page 230-R is mapped to page232-(S−1).

Embodiments of the present disclosure are not limited to direct mapping.For instance, the CDRAM device 210 can serve as an N-way associativecache. That is associativity can be used to map data from a memorydevice N-ways to a CDRAM device. The CDRAM device can be configured sothat each of the locations for a cache entry (e.g., slots) correspondingto a particular portion of data from a memory device can be mapped tothe same page in the CDRAM device. Therefore, when locating data in theCDRAM device, each location, e.g. slot, where requested data could belocated is on a same page in the CDRAM. As such, only one page needs toopened, read, and have its tag data compared to tag data from a commandto determine if the requested cache data is located at any one of thepossible locations for a cache entry in the CDRAM device thatcorresponds to a particular portion of data from a memory device.

FIG. 3 illustrates a cache entry in cache in accordance with a number ofembodiments of the present disclosure. In a number of embodiments, apage in cache, such as CDRAM, can comprise a number (e.g., multiple) ofcache entries (e.g., slots). Each slot can include a portion of datathat is cached from a memory device, along with tag data (e.g., anaddress, a valid bit, and a dirty bit). In FIG. 3, slot 340 includes tagdata which includes an address 342, a valid bit 344, and a dirty bit346. Slot 340 also includes data 348 (e.g., cache data). The address 342includes a number of bits that indicate the block, page, and slot ofslot 340. The valid bit 344 includes a bit that indicates whether thedata in the slot is valid (e.g., includes data that is currently beingcached by the CDRAM) and the dirty bit 346 includes a bit that indicateswhether the data in the slot has changed, but has not been written to abacking store. Data 348 can include a number of bits that represent thecache data stored in the slot 340.

FIGS. 4A and 4B illustrate the contents of a page in cache in accordancewith a number of embodiments of the present disclosure. In FIG. 4A,cache page 432-1 can include a number of cache entries (e.g., slot452-(M−1) and 452-M/2). Each of the slots can include tag data, whichincludes an address, a valid bit, and a dirty bit; and also cache data.For example, page 432-1 can cache data that corresponds to a first halfof a page of data from a backing store (e.g., if the page of data fromthe backing store is twice as big as cache page 432-1.

In FIG. 4B, cache page 430 can include a number of cache entries (e.g.,slot 452-(M−1) and 452-M/4). Each of the slots can include tag data,which includes an address, a valid bit, and a dirty bit, and also cachedata, along with a way index (WI). A way index (e.g. WI−1 or WI−N) canbe used to indicate a particular slot of a number of potential slots inwhich requested data could be located when CDRAM is using N-wayassociativity, for instance. In this example, page 432-2 can include anumber of slots that can each store data corresponding to a quarter of apage of data from a backing store (e.g., if the page of data from thebacking store is twice as big as cache page 432-2 and the cache page432-2 is mapped with 2-way associativity). In FIG. 4B, cache page 432-2illustrates 2-way associativity in which data corresponding to locationM−1 from a memory device (e.g., a backing store) could be located ineither of slots 452-(M−1) having corresponding way index WI−1 or WI−Nand data corresponding to location M/4 from a memory device could belocated in either of slots 452-(M/4) having way index WI−1 or WI−N. In anumber of embodiments, the CDRAM can accommodate various degrees ofassociativity (e.g., N-way associativity).

FIG. 5 illustrates a command 560 associated with an apparatus comprisingcache in accordance with a number of embodiments of the presentdisclosure. Command 560 can be a read command or a write command, forinstance. The command 560 can include a command indicator 562, whichindicates the command type (e.g., read command or write command). Thecommand 560 can also include tag data that includes an address 564,which indicates the block, page, and/or slot of the data that isassociated with the command 560. The command 560 also includes atransaction ID (TID) 566 that can be used by the cache controller and/orthe CDRAM device to identify the command corresponding to data that ispassed between the cache controller and the CDRAM device.

As an example, command 560 can be a read command can be received by aCDRAM device. The CDRAM device can process the command by locating theparticular cache page indicated in the command and opening that page. Aparticular slot indicated in the command can be located in the cachepage that was opened and tag data in the particular slot can be read.Comparison logic on the CDRAM device can be used to check if the validbit in the slot is set and if the block address in the command's addressmatches the block address bits in the slot. If the valid bit is set andthe block addresses match, then the slot can be considered a hit and theCDRAM can return a suitable response to the cache controller. Theresponse to the cache controller can include a TID and the cache datafrom the particular slot. If the valid bit is not set and/or the blockaddresses do not match, then the slot is considered a miss and the CDRAMcan return a suitable response to the cache controller (e.g., a responseindicating that the data requested in the read command was not locatedin the CDRAM).

In a number of embodiments, a CDRAM 110 can process a write command bylocating the slot indicated in the write command's address. The CDRAM(e.g., 110) can read the data at the slot and use comparators to checkif the valid bit in the slot is set and if the dirt bity is set. If thevalid bit is not set, then the data from the write command can bewritten to the slot. If the valid bit is set, but the dirty bit is notset, then the data from the write command can be written to the slot. Aresponse can be sent to a cache controller (e.g., 112) indicating thatthe write has been completed. The response can include a transaction ID(TID) which can be used by the cache controller (e.g., 112) to identifywhich particular command was completed. A determination that the validbit is set and the dirty bit is set can indicate that cache data that iscurrently in the slot needs to be evicted. Upon eviction of the cachedata from the slot, the cache data from the write command can be writtento the slot. A suitable response can then be sent to a cache controllerindicating that the write has been completed. The response can include atransaction ID (TID) and also the data and the address of the data thatwas evicted from the slot. The evicted data can be returned from theCDRAM to a backing store (e.g. memory device 120).

FIGS. 6A-6B illustrate responses to a read command associated with anapparatus comprising cache in accordance with a number of embodiments ofthe present disclosure. FIG. 6A illustrates a response 672 to a readcommand that was a hit. In FIG. 6A, response 672 includes a hitindicator 676, a transaction ID (TID) 666, and data 648. The hitindicator 676 can indicate that the data requested in the read commandwas found in the CDRAM. The transaction ID 666 can be used to identifythe command associated with the response 672. The data 648 can be thecache data requested in the read command that was read from the CDRAM.The response 672 can be sent on an output interface from a CDRAM deviceto a cache controller in response to the CDRAM device processing acommand. The CDRAM device can process a command without sending data(e.g., tag data) between the CDRAM device and the cache controllerduring processing of the command.

FIG. 6B illustrates a response 674 to a read command that was a miss. InFIG. 6B, response 674 includes a miss indicator 678 and a transaction ID(TID) 666. The miss indicator 678 can indicate that the data requestedin the read command was not found in the CDRAM. The transaction ID 666can be used to identify the command associated with the response 674.The response 674 can be sent on an output interface from a CDRAM deviceto a cache controller in response to the CDRAM device processing acommand. The CDRAM device can process a command without sending data(e.g., tag data) between the CDRAM device and the cache controllerduring processing of the command.

FIGS. 7A-7B illustrate responses to a write command associated with anapparatus comprising cache in accordance with a number of embodiments ofthe present disclosure. FIG. 7A illustrates a response 782 to a writecommand that wrote data to a slot where either the valid bit or thedirty bit was not set, e.g., data was not evicted when executing thewrite command. In FIG. 7A, response 782 includes a write completedindicator 786 and a transaction ID (TID) 766. The write completedindicator 786 can indicate that the data in the write command waswritten to the CDRAM. The transaction ID 766 can be used to identify thecommand associated with the response 782. The response 782 can be senton an output interface from a CDRAM device to a cache controller inresponse to the CDRAM device processing a command. The CDRAM device canprocess a command without sending data (e.g., tag data) between theCDRAM device and the cache controller during processing of the command.

FIG. 7B illustrates a response 784 to a write command that wrote data toa slot where the valid bit and the dirty bit was set, e.g., data wasevicted when executing the write command. In FIG. 7B, response 784includes a write completed indicator 786, a transaction ID (TID) 766,and address 742 of the data that was evicted, and the data 748 that wasevicted from a slot. The write completed indicator 786 can indicate thatthe data in the write command was written to the CDRAM. The transactionID 766 can be used to identify the command associated with the response782. The address 742 of the data that was evicted and the data 748 thatwas evicted can be read from the slot by the CDRAM device and sent tothe cache controller in the response 784 so the evicted data can bewritten to a memory device. The response 784 can be sent on an outputinterface from a CDRAM device to a cache controller in response to theCDRAM device processing a command. The CDRAM device can process acommand without sending data (e.g., tag data) between the CDRAM deviceand the cache controller during processing of the command.

The present disclosure includes apparatuses and methods for a cachearchitecture. An example apparatus that includes a cache architectureaccording to the present disclosure can include an array of memory cellsconfigured to store multiple cache entries per page of memory cells; andsense circuitry configured to determine whether cache data correspondingto a request from a cache controller is located at a location in thearray corresponding to the request, and return a response to the cachecontroller indicating whether cache data is located at the location inthe array corresponding to the request.

Although specific embodiments have been illustrated and describedherein, those of ordinary skill in the art will appreciate that anarrangement calculated to achieve the same results can be substitutedfor the specific embodiments shown. This disclosure is intended to coveradaptations or variations of one or more embodiments of the presentdisclosure. It is to be understood that the above description has beenmade in an illustrative fashion, and not a restrictive one. Combinationof the above embodiments, and other embodiments not specificallydescribed herein will be apparent to those of skill in the art uponreviewing the above description. The scope of the one or moreembodiments of the present disclosure includes other applications inwhich the above structures and methods are used. Therefore, the scope ofone or more embodiments of the present disclosure should be determinedwith reference to the appended claims, along with the full range ofequivalents to which such claims are entitled.

In the foregoing Detailed Description, some features are groupedtogether in a single embodiment for the purpose of streamlining thedisclosure. This method of disclosure is not to be interpreted asreflecting an intention that the disclosed embodiments of the presentdisclosure have to use more features than are expressly recited in eachclaim. Rather, as the following claims reflect, inventive subject matterlies in less than all features of a single disclosed embodiment. Thus,the following claims are hereby incorporated into the DetailedDescription, with each claim standing on its own as a separateembodiment.

What is claimed is:
 1. An apparatus, comprising: an array of memorycells configured to store multiple cache entries per page of memorycells; and sense circuitry configured to: determine whether cache datacorresponding to a request from a cache controller is located in atleast one of a plurality of locations in the array corresponding to therequest by: opening a single page in the array that includes a pluralityof slots where each of a plurality of ways associated with the cachedata corresponding to the request are located, wherein the single pageis mapped to a location in a memory device where data associated withthe request is located; and comparing tag data associated with theplurality of ways that is read from the single page in the cache to tagdata from the request using comparison logic located on the cache. 2.The apparatus of claim 1, wherein the apparatus is configured to returncache data corresponding to the request in response to a determinationthat the cache data is located in at least one of the plurality oflocations in the array corresponding to the request.
 3. The apparatus ofclaim 1, wherein the apparatus is configured to write cache datacorresponding to the request in the array of memory cells in response toa status of a validity indicator indicating that valid data is not in atleast one of the plurality of locations in the array corresponding tothe request.
 4. The apparatus of claim 1, wherein the apparatus isconfigured to evict dirty data from the array in response to a status ofa validity indicator indicating that valid data is in at least one ofthe plurality of locations in the array corresponding to the request. 5.The apparatus of claim 4, wherein the apparatus is configured to writecache data corresponding to the request in at least one of the pluralityof locations in the array subsequent to evicting dirty data from atleast one of the plurality of locations in the array of memory cells. 6.The apparatus of claim 1, wherein the apparatus is configured todetermine whether cache data is located in at least one of the pluralityof locations in the array corresponding to the request without sendingtag data to the cache controller.
 7. The apparatus of claim 1, whereineach cache entry of the number of cache entries are stored in one of anumber of slots on one of a number of pages of the array of memorycells.
 8. The apparatus of claim 7, wherein each cache entry of themultiple cache entries include respective cache data and tag data. 9.The apparatus of claim 7, wherein tag data comprises an addresscorresponding to a backing store, a valid bit, and a dirty bit.
 10. Theapparatus of claim 7, wherein each cache entry of the multiple cacheentries includes a respective way index.
 11. A method for operatingcache, comprising: receiving a read request from a cache controller;determining whether cache data corresponding to the read request islocated in the cache by: opening a single page in the cache, wherein thesingle page is mapped to a particular location in a memory device wherethe data corresponding to request is located and the single page;reading tag data from the single page; and comparing the tag data readfrom the single page in the cache to tag data from the read requestusing comparison logic located on the cache.
 12. The method of claim 11,wherein the method includes returning the cache data from the readrequest to the cache controller in response to a determination, by thecomparison logic, that the cache data corresponding to the read requestis located in the cache.
 13. The method of claim 11, wherein returningthe response includes providing an indication in the response thatindicates the cache data is not located in the cache in response to avalidity indicator indicating that valid data is not located in thecache at the location corresponding to the read request.
 14. The methodof claim 11, wherein returning the response includes providing anindication in the response that indicates the cache data is not locatedin the cache in response to tag data associated with the read requestnot matching tag data read from the single page.
 15. The method of claim11, wherein returning the response includes returning a transactionidentifier (TID).
 16. An apparatus, comprising: a cache comprising anarray of memory cells and sense circuitry, wherein the cache is coupledto a cache controller via an input interface and an output interface,and wherein the cache is configured to: receive a command via the inputinterface; process the command by: reading data from only a particularpage in the cache based on information in the command, where theparticular page includes a plurality of slots mapped to a location in amemory device where data corresponding to the command is located, andcomparing tag data associated with the plurality of slots read from theparticular page in the cache to tag data from the command; and return aresponse to the cache controller, via the output interface, indicatingwhether data associated with the command is located in the cache. 17.The apparatus of claim 16, wherein the sense circuitry includescomparison logic to determine if data corresponding to the command islocated in at least one of the plurality of slots in the particular pagein the cache corresponding to the command.
 18. The apparatus of claim16, wherein the cache is configured to process the command withouttransferring tag data to the cache controller.
 19. The apparatus ofclaim 16, wherein the cache is configured to process the command bychecking multiple cache entries in parallel logic from only theparticular page to determine if data corresponding to the command islocated in the cache corresponding to the command.
 20. The apparatus ofclaim 16, wherein the particular page in the cache corresponds to aparticular location in the memory device that is mapped to at least oneof a plurality of slots in the particular page in the cache where thedata corresponding to the command is also located.